Man pages describe how the system actually functions, not how a standards body N years after the OS came out changed the standard. If Red Hat chose to ship POSIX 2003 man pages with their OS, I take that as meaning that's the closest POSIX standard to what they shipped.
I would leave the OS-provided POSIX man pages alone, but download the current versions and, install them somewhere else, like /usr/local/Linuxlinux-man-pages/share/man, then put that directory into your MANPATH.
If you rename the p pages to have some other tag — say, pc for "POSIX current" — you can query them separately from the OS-provided ones. For example, you could use a tool like mmv:
$ mmv 'man1p/*.1p.gz' 'man1p/#1.1pc.gz' $ mv man1p man1pc ... do the same for man 2p, etc ... $ man ls # shows GNU ls page $ man 1p ls # shows OS-provided POSIX ls page $ man 1pc ls # shows current POSIX ls page Either remove the non-POSIX man pages that conflict with the OS-provided ones, or tag them similarly if you also want to be able to refer to current Linux-specific man pages. You could use lc for "Linux current", for example.